The present invention relates to a method of feeding groups of tobacco items, in particular cigarettes, to a continuous packing machine.
In the following description, reference will be made purely by way of example to the feeding of groups of cigarettes to said packing machine.
In the tobacco industry, reciprocating cigarette packing machines are employed, i.e. wherein the cigarettes normally travel in steps and are handled by means of reciprocating members.
Reciprocating packing machines feature an input device comprising a cigarette feedbox normally presenting at least three outlets, each defined by a number of side by side, substantially vertical channels in turn defined by a number of side by side, substantially vertical partitions.
For each outlet, the input device also comprises a fixed box for receiving a group of cigarettes composed of at least one layer, and positioned facing the bottom end of the relative channels. The input device also comprises a reciprocating push device for axially engaging the cigarettes in the group inside the box and expelling them axially from the box into a pocket on a conveyor travelling in steps in a direction perpendicular to the cigarettes inside the feedbox, and which provides for feeding the groups of cigarettes to the packing machine.
In known input devices of the above type, each cigarette, on leaving the bottom output end of the respective channel and being positioned inside the box, supports the entire column of cigarettes aligned inside the respective channel, and is positioned with a generating line contacting the bottom cigarette in the respective column. Also, both in the upper layer of the group inside the box, and in the layers defined inside the feedbox by the columns of cigarettes inside the respective channels, the adjacent cigarettes are separated slightly in a horizontal transverse direction, due to the presence of the partitions. Consequently, when the group of cigarettes inside the box is moved in a substantially horizontal, transverse direction in relation to a fixed bottom layer, i.e. in relation to the layer defined by the bottom cigarettes in the respective columns, each cigarette in the bottom layer automatically moves into a pocket defined beneath, and by the two columns separated by, each partition, and at the same time the cigarettes in the respective columns drop down once more into contact with the cigarettes in the upper layer.
As such, a minimum amount of lateral movement of the group of cigarettes inside the box is sufficient to offset the cigarettes in relation to those in said bottom layer, and to clamp them transversely in the offset position, so that, with known feed devices, the cigarettes in said group can only be expelled purely axially.
In the case of a reciprocating packing machine, the above limitation poses no real inconvenience, in that, during expulsion, the pocket of the conveyor supplying the packing machine is stationary and aligned with the box. In the case of a continuous packing machine, on the other hand, the above limitation poses serious drawbacks involving the use of complex pocket type feed conveyors travelling in steps at the input feedbox, and continuously at an unloading station where the groups of cigarettes are unloaded on to a continuously operating follow-up portion of the packing machine.